1. Field of the Invention
This invention relates to a fleet management server, onboard terminal equipments and a fleet management system for mining haulage vehicles, and specifically to a reduction in the amount of wireless communications to be used in fleet management.
2. Description of the Related Art
As a control method for mining haulage vehicles, so-called “blocking control” that divides a travel route for the individual haulage vehicles into plural travel segments and permits only one of the haulage vehicles to travel in each travel segment may be performed (see JP-A-2009-61892).
On the other hand, mining haulage vehicles are loaded at a loading site with earth, sand and/or ore (hereinafter collectively called “rock”) from a loading machine such as a wheel loader or hydraulic excavator. Until loading work is completed for a vehicle ahead of one's own vehicle, however, the own vehicle stops and waits before the loading site. According to a fleet management system that relies upon blocking control as a premise, the stop of the front vehicle for its turn to access the loading site, therefore, prevents the own vehicle, which is located behind the front vehicle, from entering a travel segment allocated to the front vehicle so that the own vehicle needs to stop at a position rear of the travel segment. As a result, plural haulage vehicles may form a queue for waiting their turn before the loading site.
As an illustrative control method for the queue of the stopped haulage vehicles, U.S. Pat. No. 5,586,030 is known. U.S. Pat. No. 5,586,030 discloses an autonomous traveling vehicle system that, when the most forward position in a queue is vacated in a first-in, first-out manner, allows the rear vehicles to move to new positions sequentially.
According to the autonomous traveling vehicle system of U.S. Pat. No. 5,586,030, request signals that request next stop positions are transmitted to the server sequentially, first from the frontmost haulage vehicle. The transmission of these request signals is conducted even in a situation that the frontmost vehicle is at stop. A situation, therefore, arises in which the server cannot instruct the next stop positions in response to the request signals. Because the request signals at this time are transmitted to the server although they are unnecessary wireless communications from the viewpoint of forward movements of the haulage vehicles, the autonomous traveling vehicle system of U.S. Pat. No. 5,586,030 involves a problem in that such necessary request signals induce an increase in the amount of communications at a wireless communication base station and also an increase in the processing load on the server.
With the foregoing circumstances in view, the present invention has, as objects thereof, the provision of a fleet management server, onboard terminal equipments and a fleet management system, which can perform fleet management while suppressing the occurrence of unnecessary wireless communications that do not contribute to forward movements of haulage vehicles.